• IPv4 : Internet protocol version 4
• IPv4 address is of 4 bytes in length each octet of 1 byte.
• In ipv4 their are 4 number separated by dot each of them is called octet. 192.168.1.22

IP address in binary. ip-to-binary 192 = 11000000, 168 = 10101000 , 1 = 00000001 , 22 = 11111110 its difficult to read binary no. so we write it in dotted decimal like this 192.168.1.22

192.168.1 = network ID 22 = is host ID (only in class c) it change according to classes. network portion is same in local network only the host address is different .

Reference

• Total 4,294,967,296 4 billion IPV4 are their. why only 4 billion ipv4 address?

IPv4 addresses are (4 bytes) 32 bits long, which allows for a total of 2^32 possible addresses.

• To manage these 4 billion IP IP address classes are introduce. Here’s a table summarizing the IP address classes:

Class	Range	Leading Bits	Subnet Mask	Hosts per Network	Usage
A	0.0.0.0 to 127.255.255.255	0	255.0.0.0	~16 million	Very large networks
B	128.0.0.0 to 191.255.255.255	10	255.255.0.0	~65,000	Medium to large networks
C	192.0.0.0 to 223.255.255.255	110	255.255.255.0	Up to 254	Small networks
D	224.0.0.0 to 239.255.255.255	1110	N/A	N/A	Multicast address
E	240.0.0.0 to 255.255.255.255	1111	N/A	N/A	Experimental purposes

Type	Range	Usage
Private IP Addresses	10.0.0.0 to 10.255.255.255	Internal networks
	172.16.0.0 to 172.31.255.255	Internal networks
	192.168.0.0 to 192.168.255.255	Internal networks
Loopback Address	127.0.0.1	Testing and internal communications

Class	Bits	Network	Host	Subnet Mask
A	8 bits	Network (1st Octet)	24 bits (3 Octets)	/8 or 255.0.0.0
B	16 bits	Network (1st & 2nd)	16 bits (2 Octets)	/16 or 255.255.0.0
C	24 bits	Network (1st, 2nd, & 3rd)	8 bits (1 Octet)	/24 or 255.255.255.0

class	starting address	ending address
A	0.0.0.0	127.255.255.255
B	128.0.0.0	191.255.255.255
C	192.0.0.0	223.255.255.255

Find the following:

1. Network address: 43.0.0.0 as /8 indicate class A and it have 1 octet of network and 3 are host octet
2. Maximum number of hosts in the network: 16,777,214 3 host octet that have 24 bites so max host is 2^24 and sub 2.
3. Network broadcast address: 43.255.255.255 last addrss of network
4. First usable address of the network: 43.0.0.1 first ip - 1 to get first usable ip of network
5. Last usable address of the network: 43.255.255.254 last ip - 1 to get last useable ip of network

To find it see the first Octet of the IP address. example: 1.2.3.4 first octet is 1 and it belong to class A. 191.168.1.12 first octet is 191 and it belong to class B 192.168.1.12 first octet is 192 and it belong to class C

• The network address CANNOT be assigned to a host. network address is first address of network like 192.168.1.1

Address range 127.0.0.0 to 127.255.255.255 Used to test the network stack' (think OSI, TCP/IP model) on the local device.

Class	First Octet Range	Leading Bits	Prefix Length	Subnet Mask
A	0 - 127	0xxxxxxx	/8	255.0.0.0
B	128 - 191	10xxxxxx	/16	255.255.0.0
C	192 - 223	110xxxxx	/24	255.255.255.0

• Class A:

  • First Octet: 0 to 127
  • Prefix Length: /8 (8 bits for the network)

• Class B:

  • First Octet: 128 to 191
  • Prefix Length: /16 (16 bits for the network)

• Class C:

  • First Octet: 192 to 223
  • Prefix Length: /24 (24 bits for the network)

Class A have much host and less network Class C have much Network and less host.

Class	Number of Networks	host id	Prefix Length	Subnet Mask
Class A	128 (2^7)	16,777,216 (2^24)	/8	255.0.0.0
Class B	16,384 (2^14)	65,536 (2^16)	/16	255.255.0.0
Class C	2,097,152 (2^21)	256 (2^8)	/24	255.255.255.0

A netmask, also known as a subnet mask.

Sub netting is done to make a big network into small networks.

• Netmask define the network portion and host portion of an IP address.

In a typical IPv4 address, such as 192.168.1.1, the netmask might look like 255.255.255.0. This means that the first three octets (255.255.255) represent the network, while the last octet (0) is used for host addresses within that network.

prefix length / Netmask : is a 32-bit number

Class	CIDR	Subnet Mask
Class A	/8	255.0.0.0
Class B	/16	255.255.0.0
Class C	/24	255.255.255.0

CIDR (Classless Inter-Domain Routing) is a notation used to specify IP addresses and their associated routing prefix. It represents the number of bits in the subnet mask.

CIDR help to write ip address and sub netmask together in short form.

Netmasks can also be expressed in CIDR (Classless Inter-Domain Routing) notation, which indicates the number of bits in the subnet mask. For example, the netmask 255.255.255.0 can be represented as /24, meaning the first 24 bits are used for the network address.

• To find max host, as we know is host octet is 1 that mean 8 bite so to get /8 netmask max host 2^8 and subtract 2 from it.

• as we know is host octet is 2 that mean 16 bite so to get /16 netmask max host 2^16 and subtract 2 from it.

ip 192.168.1.1 for router. ip 192.168.1.254 is used as broadcasting address.

IPv6 have 2^128 ip addresses , sufficient for 50-60 years.

• IPv6 provide Realtime data transmission
• IPv6 provide Authentication so anyone can't send a mess on the behalf of someone else.
• Enable encryption : In IPv6 if even application layer don't encrypt data IPv6 do it.
• IT is fast than IPv4 as it IPv6 has a more streamlined header compared to IPv4, which reduces the processing time for routers and devices.

IPv6 is need because as increasing in IOT device IPv4 don't have sufficient ip address.

The first 64 bits identify the network and the last 64 bits identify the host.

fc00:1948:0420:0000:0000:0000:0000:0001 The Network portion is in blue and the host portion is in red. In IPv6, a /64 is recommended not only for management ease but because stateless auto configuration requires it. If you want a network smaller than a /64 (yes it is technically possible), you better use DHCPv6. However, keeping /64s is the recommended best practice.

Just like in IPv4, IPv6 addresses can be assigned dynamically or statically:

• Dynamic Host Configuration Protocol (DHCP): DHCP servers automatically assign IPv6 addresses to devices on a network. This simplifies address management for a large number of devices.

• Static IP Addresses: These addresses are manually configured and remain constant for specific devices like servers or routers.

Network Address Translation (NAT)

• NAT allows multiple devices on a local network to share a single public IP address when accessing the internet.
• This conserves the limited number of available IP addresses and enhances security by hiding internal IP addresses.

1. Static NAT:

   • Maps a single private IP address to a single public IP address.
   • Useful for servers that need a constant IP address for external access (like a web server).

2. Dynamic NAT:

   • Maps a private IP address to a public IP address from a pool of public addresses.
   • The mapping is temporary; when the session ends, the public address can be reassigned to another internal device.

Protect against Ip spoofing attack by verifying source and destination Ip address.

Port Address Translation (PAT) is a specific type of Network Address Translation (NAT) that allows multiple devices on a local network to be mapped to a single public IP address, but with a different port number for each session.

• AT translates private IP addresses and their corresponding port numbers into a single public IP address with different port numbers. This allows multiple devices to share the same public IP while maintaining separate sessions.

Translation Table: The router maintains a table like this:

Internal IP	Internal Port	Public IP	Public Port
192.168.1.2	5000	203.0.113.5	10000
192.168.1.3	5001	203.0.113.5	10001
192.168.1.4	5002	203.0.113.5	10002

Explanation

DHCP automates by assigning Ip address to device on the network when a device connects to a network, it sends a Dhcp request , and the Dhcp server dynamically assigns an available Ip address along with over network configuration parameters.

APIPA is a callback mechanism used when a device cannot obtain an Ip address from DHCP.

It assign a temporary IP address from the reversed APIPA range (169.154.0.1) to 169.254.255.224 to Facaliates local network communication